The invention relates to a method for operating a fuel tank-device for a motor vehicle, with a fuel tank to which a tank ventilation line is assigned, and with a tank shutoff valve for adjusting a flow-through cross section of the tank ventilation line, wherein the tank shutoff valve can be or is impinged with a first electric voltage for adjusting a first flow-through cross section, and with a second electric voltage for adjusting a second flow-through cross-section. The invention also relates to a fuel tank device.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
In motor vehicles a fuel tank device of the above type is for example assigned to the motor vehicle or forms a component of the motor vehicle. It serves in particular for receiving or temporarily storing an operating medium, for example the fuel. For this purpose the fuel tank device has a fuel tank, in which the fuel can be stored. During operation of the internal combustion engine the fuel is withdrawn from the fuel tank and is conducted to the internal combustion engine for operation of the internal combustion engine.
For example due to environmental influences it may be necessary to ventilate the fuel tank, i.e., to discharge a gas, for example a fuel-air-mixture, from the tank. This is in particular the case when the internal combustion engine is a component of a hybrid drive device, because the internal combustion engine oftentimes has standstill phases in which it is not operated. Correspondingly the fuel or the fuel-air-mixture is not withdrawn from the fuel tank, at least not through a fuel line.
For ventilating the fuel tank, the tank ventilation line is provided, which is assigned to the fuel tank. The tank ventilation line is fluidly connected with the fuel tank or an interior of the fuel tank, so that the gas contained in the fuel tank can be discharged through the tank ventilation line, for example in the direction of an external environment of the motor vehicle and/or in the direction of the internal combustion engine. For performing the ventilation in a controlled manner the tank shutoff valve is provided. The latter serves for adjusting a desired flow-through cross-section of the tank ventilation line. By means of the tank shutoff valve, the tank ventilation line can be completely blocked, wherein the flow-through cross section is equal to zero, or at least partially, in particular completely released.
For adjusting the desired flow-through cross-section the tank shutoff valve is impinged with a corresponding electric voltage. For example for adjusting the first flow-through cross-section the first electric voltage is used and for adjusting the second flow-through cross-section the second electric voltage is used. The second flow-through cross-section is hereby different from the first flow-through cross-section; Also the second electric voltage is different from the first electric voltage.
For example the first flow-through cross-section is equal to zero, so that when the first flow-through cross-section is given, the tank ventilation line is completely blocked. The second flow-through cross-section corresponds for example to a completely open tank ventilation line and thus to a maximal flow-through cross-section. The first electric voltage can also be equal to zero, while the second electric voltage causes the opening of the tank ventilation line, in particular a complete opening.
It would be desirable and advantageous to provide a method for operating a fuel tank device for a motor vehicle, which, is improved compared to other methods and in particular improves the acoustics of the tank shutoff valve and/or increases the service life of the tank shutoff valve.